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Discussion Starter · #1 ·
I’ll preface this by saying, I am a car enthusiast trying to learn and I’ve only done the basics like oil changes, spark plugs, and brakes. So forgive any mistakes in this post and please correct anything you think is wrong. I can’t thank you guys enough for the information on this forum! I had two independent problems, and I’ll address both separately (it will be long, but maybe someone will benefit from my experience, and the underlined text is my solution if you don't want to read the whole thing for context). Both are transmission related on a 2005 330ci, 100k miles, automatic.

First issue: Limp Mode. The car entered into a limp mode (yellow cog) a month into ownership, and steadily increased in frequency over a week (P0734 Incorrect Gear Ratio 4 code, and a P0700 generic transmission fault code). I took everyone’s advice here, and had the original battery tested, it was bad, so I purchased a new equivalent Bosch battery. This did not fix the issue, which spun me off into a whole other troubleshooting direction unnecessarily. I changed the transmission fluid, which was a little dark, but had no metal flakes. I cleaned the transmission wiring harness, cleaned the MAF sensor, inspected the alternator, fuses, and cleaned the wheel speed sensors. I then spent $550 at what I thought was a good local BMW indy shop (full of M3’s, M5’s etc), who replaced solenoids, reset the transmission control module (TCM), and kept my car for over a month trying to figure out the problem. Ultimately, they said I needed a new/used transmission ($2400 total). When I went to pick the car up, they had to jump-start it, and the (new Bosch) battery tested bad. I just shook my head and took the car. Why this BMW specialist didn’t check the battery first is beyond me… so the NEW battery while displaying proper voltage, actually had a bad cell as it was explained to me (lucky guy right?), and the second new battery solved the limp mode. So if you replace the battery and that doesn’t work, exchange it and try again! Below 12.5 volts, this could be the problem, like previously stated on this forum.

Second issue: Delayed Upshift. So right after the limp mode was fixed, there was a three second delay in the upshift from third to fourth gear in all modes of operation (normal, sport, and “manual”). I decided to take it to a dealer (I know), to have them do a diagnostic. It came back with EGS: Gear Monitoring 4 (This was in the history and not an active code), and EGS: CAN Torque Reduction. Once again, I was told with a straight face I needed a new transmission at $7,000 this time, and I needed to replace the right front tire since it was unevenly worn (foreshadowing here…). I asked them to explain why those codes led them to believe I needed a new transmission, and they just said, “that's what the computer says.” Ok I’ll get right on that $7k transmission job. I was still convinced it was an electrical issue at this point.

Eventually, I stumbled across what looked to be a BMW technician training document that described the whole transmission system logic. One of the things it states is to check for 12.5 battery voltage (see limp mode above) and check for uneven tire wear for any transmission related issue. Furthermore, it described the AGS Curve Recognition software,

“This feature will inhibit upshifts when the vehicle is in a curve. This is to improve stability when the vehicle is cornering at high speeds. The TCM will initiate this feature when it detects a difference between left and right (front) wheel speed signals. The difference in these signals will indicate that the vehicle is in a curve. Be aware that improper tire sizes, brands and inflation pressures can influence this feature. Always address these issues first when diagnosing delayed upshift complaints.”

So I think this was my smoking gun. I began to address the issues which might lead the wheel speed sensors to have a discrepancy between the two front wheels. I tested the wheel speed sensors first, which produced voltage when the tire turned. The two passenger side wheels were bent, the right front was barely within limits to be fixed but the wheel shop managed to straightened them. I bought two new all-season Continental front tires to match the rears (side note the front tires were summer continentals and the rears were all-season continentals, staggered setup), and had an alignment done at a pro tuning shop (2.5hrs). This did not fix the problem, but my goal was to get the car right since it was in good shape and despite the problems, I was already blindly in love with it. Worst case my buddy would help me swap a used transmission in.

At this point I took a break from troubleshooting and began to address the vibration under braking I noticed after the wheels were straightened. Upon inspection the brakes had plenty of pad remaining, but the right front rotor was scorched on the inside with deposits and the caliper was just not sitting right. This was also the unevenly worn tire and I had such a hard time turning that rotor compared to when the tire was on. So my best guess is the dragging brake, suspension misalignment, unevenly worn tires, and bent wheels, were contributing factors creating the wheel speed difference, thereby creating the delayed upshift. I changed the brakes, rotors, fluid, and the delayed upshift remained until about 200 miles before it gradually went away. I believe I have read somewhere the TCM takes a while to adapt to changes, about 200-300 miles, maybe someone can confirm this.

Had I not researched this through the help of this forum, I may have ended up with a used transmission with the same problem, but $2,400+ lighter in my pocket. In the end, the transmission was doing exactly what it was programmed to do; external factors caused the problem. I can’t definitively say what fixed the problem, but this is my best guess. Let me know if you have any questions; attached are the documents I found for reference that helped.
 

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Thank you so much for the wonderful post. I am facing the first two codes as well. Car drives perfect around town and no slips whatsoever. I believe my issue is also electrically related but I haven't invested enough time to solve cause I mainly drive in the city.

Did you ever experience a symptom where the car would go into limp mode when you braked hard on the highway? ( Ie if you were driving at 110km/h and all of sudden had to brake, did your car to into limp mode with the two tranny codes that u mentioned in addition to CAN torque reduction? This is the problem that I am facing tight now)



I’ll preface this by saying, I am a car enthusiast trying to learn and I’ve only done the basics like oil changes, spark plugs, and brakes. So forgive any mistakes in this post and please correct anything you think is wrong. I can’t thank you guys enough for the information on this forum! I had two independent problems, and I’ll address both separately (it will be long, but maybe someone will benefit from my experience, and the underlined text is my solution if you don't want to read the whole thing for context). Both are transmission related on a 2005 330ci, 100k miles, automatic.

First issue: Limp Mode. The car entered into a limp mode (yellow cog) a month into ownership, and steadily increased in frequency over a week (P0734 Incorrect Gear Ratio 4 code, and a P0700 generic transmission fault code). I took everyone’s advice here, and had the original battery tested, it was bad, so I purchased a new equivalent Bosch battery. This did not fix the issue, which spun me off into a whole other troubleshooting direction unnecessarily. I changed the transmission fluid, which was a little dark, but had no metal flakes. I cleaned the transmission wiring harness, cleaned the MAF sensor, inspected the alternator, fuses, and cleaned the wheel speed sensors. I then spent $550 at what I thought was a good local BMW indy shop (full of M3’s, M5’s etc), who replaced solenoids, reset the transmission control module (TCM), and kept my car for over a month trying to figure out the problem. Ultimately, they said I needed a new/used transmission ($2400 total). When I went to pick the car up, they had to jump-start it, and the (new Bosch) battery tested bad. I just shook my head and took the car. Why this BMW specialist didn’t check the battery first is beyond me… so the NEW battery while displaying proper voltage, actually had a bad cell as it was explained to me (lucky guy right?), and the second new battery solved the limp mode. So if you replace the battery and that doesn’t work, exchange it and try again! Below 12.5 volts, this could be the problem, like previously stated on this forum.

Second issue: Delayed Upshift. So right after the limp mode was fixed, there was a three second delay in the upshift from third to fourth gear in all modes of operation (normal, sport, and “manual”). I decided to take it to a dealer (I know), to have them do a diagnostic. It came back with EGS: Gear Monitoring 4 (This was in the history and not an active code), and EGS: CAN Torque Reduction. Once again, I was told with a straight face I needed a new transmission at $7,000 this time, and I needed to replace the right front tire since it was unevenly worn (foreshadowing here…). I asked them to explain why those codes led them to believe I needed a new transmission, and they just said, “that's what the computer says.” Ok I’ll get right on that $7k transmission job. I was still convinced it was an electrical issue at this point.

Eventually, I stumbled across what looked to be a BMW technician training document that described the whole transmission system logic. One of the things it states is to check for 12.5 battery voltage (see limp mode above) and check for uneven tire wear for any transmission related issue. Furthermore, it described the AGS Curve Recognition software,

“This feature will inhibit upshifts when the vehicle is in a curve. This is to improve stability when the vehicle is cornering at high speeds. The TCM will initiate this feature when it detects a difference between left and right (front) wheel speed signals. The difference in these signals will indicate that the vehicle is in a curve. Be aware that improper tire sizes, brands and inflation pressures can influence this feature. Always address these issues first when diagnosing delayed upshift complaints.”

So I think this was my smoking gun. I began to address the issues which might lead the wheel speed sensors to have a discrepancy between the two front wheels. I tested the wheel speed sensors first, which produced voltage when the tire turned. The two passenger side wheels were bent, the right front was barely within limits to be fixed but the wheel shop managed to straightened them. I bought two new all-season Continental front tires to match the rears (side note the front tires were summer continentals and the rears were all-season continentals, staggered setup), and had an alignment done at a pro tuning shop (2.5hrs). This did not fix the problem, but my goal was to get the car right since it was in good shape and despite the problems, I was already blindly in love with it. Worst case my buddy would help me swap a used transmission in.

At this point I took a break from troubleshooting and began to address the vibration under braking I noticed after the wheels were straightened. Upon inspection the brakes had plenty of pad remaining, but the right front rotor was scorched on the inside with deposits and the caliper was just not sitting right. This was also the unevenly worn tire and I had such a hard time turning that rotor compared to when the tire was on. So my best guess is the dragging brake, suspension misalignment, unevenly worn tires, and bent wheels, were contributing factors creating the wheel speed difference, thereby creating the delayed upshift. I changed the brakes, rotors, fluid, and the delayed upshift remained until about 200 miles before it gradually went away. I believe I have read somewhere the TCM takes a while to adapt to changes, about 200-300 miles, maybe someone can confirm this.

Had I not researched this through the help of this forum, I may have ended up with a used transmission with the same problem, but $2,400+ lighter in my pocket. In the end, the transmission was doing exactly what it was programmed to do; external factors caused the problem. I can’t definitively say what fixed the problem, but this is my best guess. Let me know if you have any questions; attached are the documents I found for reference that helped.
 

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Discussion Starter · #3 ·
jarjar

No problem. I would get your battery tested at a local auto parts store. I did mine at Pep Boys for free; it may take them 30 min. I had an AGS type battery and I believe they may read a normal voltage with a multi-meter but still have a bad cell. If the battery is ok, then check the alternator. I believe it should be showing 14.1volts+, engine running.

As far as hard braking causing the limp mode, I'm really not sure. I know when my limp mode problem began, I managed it by first letting the car idle for 10 min giving the alternator a chance to charge the battery, it would go into limp mode once, I'd pull over, restart and it would be ok the rest of the day. But it got worse over time.

There are a lot of variables surrounding the situation you described. Maybe there are certain situations in which the system (battery/alternator) just isn't providing enough voltage to the transmission control module (the transmission's brain), which causes it to protect itself by going into safe mode. Just speculating here.
 

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Discussion Starter · #5 ·
Ha! Thanks man, I'd like to say I'm that creative but I think I've seen that username on some Formula 1 forum probably.
 

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Thanks for sharing as I will be looking at helping a friend with her 2005 325i with about 101K miles with limb mode and cog light
 

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just wondering why would the battery cause the limp mode? doesnt the alternator takes over once the car starts? the battery's role is ot provide the juice for the starter. so i doubt a bad battery will cause limp modes. a bad battery will lose cranking power and ability to receive and hold charge
 

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just wondering why would the battery cause the limp mode? doesnt the alternator takes over once the car starts? the battery's role is ot provide the juice for the starter. so i doubt a bad battery will cause limp modes. a bad battery will lose cranking power and ability to receive and hold charge
Probably cause the E46 hates low battery voltage and will do many crazy things due to it
 
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